This invention relates to wood chipping machinery, and is particularly useful for chipping disintegrators for stumps and other wood debris as disclosed in U.S. Pat. Nos. 4,736,781 and 4,771,953.
As explained in the above patents, the problem of disposal of certain types of materials such as stumps, wood debris from old lumber, limbs, roots, pallets and other such items is becoming more severe. Those landfill businesses that are still operational increasingly will not accept these materials. The alternative of burning them is often outlawed. Leaving these items on site is aesthetically unappealing and usually contrary to zoning regulations. Consequently, machines of the type in the above patents have proven highly desirable for reducing large items such as stumps, etc. to chips which have definite utility and are disposable.
Because such items do not typically comprise just clean wood, e.g. stumps and limbs have sand, stones and the like clinging to them, discarded pallets have nails, clips and other metal fasteners therein, and old lumber as from demolished buildings has metal spikes, nails, electrical wiring and the like clinging thereto and embedded therein, the chipper is subjected to rigorous conditions. One item subjected to particular wear is each of the several chipping knives. Another significant wear area, however, has been found to be on the disc itself, just upstream of the slot adjacent each knife mounting pocket and through which the chips pass as they are formed by the action of the knife with the anvil.
As the knives wear, they can be reversed and/or rotated to expose sharp edges, and ultimately replaced. Too frequent replacement involves considerable added expense. Chipping with dulled and broken knives, however, requires greatly increased energy input, causes expensive heat generation at the wood, and slows production drastically. Therefore, knives are frequently replaced even though expensive. It would be greatly advantageous to delay wear of the knives. As to disc wear upstream of the knife pockets, this results in poor chipping action, greater wear of the knives and holders, and even destruction of the knife holders and mounting pockets. It ultimately necessitates extensive repair to or replacement of the large, heavy and expensive disc.